Effect of Cu^2＋ on K^＋ Current in Acutely Isolated Rat Hippocampal Neurons by Whole Cell Patch Clamp Technique

Using the whole cell patch clamp technique, the effect of Cu^2＋on transient outward K^＋current （/to） and delayed rectifier K^＋ current （Idr） was studied in acutely isolated rat hippocampal neurons.Ito and Idr were increased when the concentration of Cu^2＋ was lower than 2 × 10^-5 and 10^-5 tool/L, respectively, and increased ratio was decreased with increasing Cu^2＋concentration in the bath solutions. When the concentration continued to increase to 5× 10^-5 and 2 × 10^- 5 mol/L, the currents were hardly changed, while the concentration was more than 10^-4 and 5 × 10^-5 mol/L, the currents were inhibited remarkably. Cu^2＋ （10^-5 mol/L） did not affect the activation and inactivation process of Ito. The activation curve of Idr was shifted toward positive potential, but 10^-5 mol/L Cu^2＋did not affect slope factor. According to these results, it was considered that Cu^2＋at low concentration in the bath solution could promote Ito and Idr while at high concentration could inhibit them, and change of amplitude was different with different membrane voltage. Conclusion was drawn： Cu^2＋may be involved in the pathophysiologic mechanism of diseases with neuropathological components.

In vivo patch clamp recording technique in the study of neurophysiology

The patch clamp recording technique in vivois a blind patch clamp recording methods to record the current of the spinal or cereral neurons of anaes：hesia （ or awake） animals. This technique can be used to study the synaptic function and plasticity in central nervous system in vivoin order to understand the physiological properties of the ion channels from an integrated point of view. The advantage of this technique have already presented itself in the study of the synaptic transmission and nervous network. Nowadays, in vivo patch whole-cell recording technique in combination with other techniques is becoming a common method in the research fields.

The Reconstructing of Low Signal-noise Ratio Single Ion Channel Signal from Patch-clamp Recordings Sampled in the Colored Background Noise

The single ion channel signal is an ionic current that can be recorded by the patch clamp technique. Hidden Markov model (HMM) algorithm has been used to convert the low signal noise ratio (SNR) noisy recording into an idealized quantal one in the case of white background noise. The traditional HMM algorithm is extended and adapted to the colored background noise. A new algorithm called EHMM (Extended HMM) algorithm is proposed, and mainly validated by simulation. Results show that it’s effective.

The Effect of Benzyltetrahydropalmatine (BTHP) on Action Potentials and the Two Components of Delayed Rectifying Potassium Currents in Guinea Pig Ventricular Myocytes

The effects of BTHP on Ca 2+ independent action potential and the two components of delayed rectifier potassium currents were studied in guinea pig single ventricular myocytes by using whole cell patch clamp technique. BTHP 30 μmol·L -1 significantly prolonged APD 90 from 143±16 ms to 184±21 ms ( P 【0.01, n=5) without affecting either the RP or APA, and the APD prolonging effects of BTHP were independent of extracellular Ca 2+ . BTHP inhibited both I kr (IC 50 =7 9 μmol·L -1 ) and I ks (IC 50 =22 4 μmol·L -1 ) in a concentration dependent fashion. The results demon strated that BTHP had no obvious selectivity for I kr and I ks .

Effect of the ginsenoside Rb1 on the spontaneous contraction of intestinal smooth muscle in mice

AIM: To investigate the effect and the possible mechanism of ginsenoside Rb1 on small intestinal smooth muscle motility in mice. METHODS: Intestinal smooth muscle strips were isolated from male ICR mice (5 wk old), and the effect of ginsenoside Rb1 on spontaneous contraction was recorded with an electrophysiolograph. The effect of ginsenoside Rb1 on ion channel currents, including the voltage-gated K + channel current (IK V ), calcium-activated potassium channel currents (IK Ca ), spontaneous transient outward currents and ATP-sensitive potassium channel current (IK ATP ), was recorded on freshly isolated single cells using the whole-cell patch clamp technique. RESULTS: Ginsenoside Rb1 dose-dependently inhibited the spontaneous contraction of intestinal smooth muscle by 21.15% ± 3.31%, 42.03% ± 8.23% and 67.23% ± 5.63% at concentrations of 25 μmol/L, 50 μmol/L and 100 μmol/L, respectively (n=5,P<0.05). The inhibitory effect of ginsenoside Rb1 on spontaneous contraction was significantly but incompletely blocked by 10 mmol/L tetraethylammonium or 0.5 mmol/L 4-aminopyridine, respectively (n=5, P<0.05). However, the inhibitory effect of ginsenoside Rb1 on spontaneous contraction was not affected by 10 μmol/L glibenclamide or 0.4 μmol/L tetrodotoxin. At the cell level, ginsenoside Rb1 increased outward potassium currents, and IK V was enhanced from 1137.71 ± 171.62 pA to 1449.73 ± 162.39 pA by 50 μmol/L Rb1 at +60 mV (n=6, P<0.05). Ginsenoside Rb1 increased IK Ca and enhanced the amplitudes of spontaneous transient outward currents from 582.77 ± 179.09 mV to 788.12 ± 278.34 mV (n=5, P<0.05). However, ginsenoside Rb1 (50 μmol/L) had no significant effect on IK ATP (n=3, P<0.05). CONCLUSION: These results suggest that ginsenoside Rb1 has an inhibitory effect on the spontaneous contraction of mouse intestinal smooth muscle mediated by the activation of IK V and IK Ca , but the K ATP channel was not involved in this effect.

Sex Difference in the Repolarization Currents of Rabbit Ventricular Cells

The current difference between male and female rabbit ventricular myocytes was investigated for elucidating the mechanism of longer QT interval and higher incidence of drug-associated torsade de pointes in female rabbits than in male rabbits. Whole cell patch clamp technique was used to record APD, I_to, I_K,tail, I_K1 and I_Ca,L of myocytes from left ventricular apex. There was no difference in the membrane capacitance between male and female rabbit myocytes. APD_90 was longer in female rabbits (560.4±26.5 ms, n=15) than in male ones (489.0±20.7 ms, n=14), P<0.05. In female rabbit myocytes, I_K,tail, I_to, I_K1 and I_Ca,L were 0.71±0.05 pA/pF (n=17), 8.28±1.03 pA/pF (n=18), 24.5±3.6 pA/pF (n=12) and 9.0±2.3 pA/pF (n=15) respectively. In male rabbit myocytes, they were 0.84±0.07 pA/pF (n=18), 8.60±1.20 pA/pF (n=18), 25.9±4.5 pA/pF (n=14) and 9.3±2.6 pA/pF (n=16) respectively. I_K,tail in female rabbits was significantly lower than that of male rabbits (P<0.05), but there was no difference in I_to, I_K1 and I_Ca,L between male rabbits and female rabbits (P>0.05). The lower I_K,tail of female rabbit myocytes may contribute to the longer repolarization and the higher incidence of drug-associated torsade de pointes.

Effect of simulated ischemia-reperfusion on I_f in sinoatrial node cells and the intervention of KATP channel opener

Objective: To study the effect of simulated ischemia-reperfusion (I/R) on If of sinoatrial node (SAN) cells and the intervention of KATP channel opener Pinacidil. Methods: The SAN cells of the neonatal rats were detached and purified 2 d before the experiment. The experimental animals were randomly divided into the control group, group of simulated I/R, group intervened with KATP channel opener Pinacidil (P+ I/R) and group intervened with KATP channel blocking agent 5-HD (5-HD + P + I/R & 5-HD + I/R). The If density of each group was measured by technique of routine whole cell patch clamp and multiple-catheter perfusion system and the If activated curve in each group was drawn. Results: ①Under different directive potentials, the If density of the SAN cells in I/R group increased significantly, compared with that in the control group ( P < 0.01); that in P + I/R group decreased significantly, compared with that in I/R group ( P < 0.01); the If density values in 5-HD + P + I/R group and 5-HD + I/R group increased significantly, compared with that in P + I/R group, but showed no significant difference with that in I/R group. ②Compared with that in the control group, the If activated curve of the SAN cells moved rightwards under ultimate activating potential, half of which was from - 108.0 ± 12.4 to - 89.5 ± 7.2 mV ( P <0.01); compared with that in I/R group, If activated curve of the SAN cells moved leftwards under ultimate activating potential, half of which was the range from -99.5± 10.8 mV (P<0.05); KATP channel blocking agent 5-HD could block the effect of Pinacdil on If activated curve. Conclusion: KATP channel opener Pinacidil can antagonize the effect of simulated I/R on the If of SAN cells, which may be beneficial to the maintenance of the relative stability of ion steady state and electrophysiological activities under condition of simulated I/R.

Gender difference of transmural heterogeneity of calcium current in rabbit ventricle

Objective: To study the distribution of I_ Ca,L in endomyocardium(Endo), mid-myocardium(Mid) and epicardium(Epi) in female and male rabbit ventricle and to elucidate the mechanism of sex difference in drug-associated torsade de pointes. Methods: Whole-cell patch clamp technique was used to record action potential and I_Ca,L. Results: Action potential duration ofMidinfemale rabbit heart waslonger thanthat in male and transmural dispersion of repolarization in female was largerthan thatinmale. The densities of I_ Ca,L in Endo, Mid and Epi of female rabbits were (7.1±0.6), (10.4±0.9) and (9.6±1.1) pA/pF and they were (9.1±0.9), (10.5±1.0) and (9.8±0.9) pA/pF in male respectively. Transmural heterogeneity of I_ Ca,L in female ventricle was more significant than that in male rabbit.Conclusion:Female rabbitspossessmoresignificant transmural heterogeneityof I_Ca,L,whichmaybe responsiblefor largertransmuraldispersion of repolarization and more drug-associated torsade de pointes in female.

Sodium channels in the apical membrane of human nasal epithelial cells

Objective To study the electrophysiological properties of sodium channels in the apical membrane of human nasal epithelial cells Method Nasal epithelial cells of human inferior turbinate from patients with obstructive sleep apnea syndrome were cultured in serum free medium on collagen gel coated membranes at an air liquid interface and studied by a patch clamp technique Results In cell attached patches, a typical single channel current with a conductance of 21 09?pS and reversal potential of -50 96 were recorded The permeability ratio P Na /P K was more than 5 80 In the presence of 10 4 mmol/L amiloride in the pipette, the incidence of sodium channels decreased from 26 67% to 5 13% This revealed that a population of channels were inhibited by amiloride at a dose of 10 4 mmol/L Ca 2+ at dose of 10 3 mmol/L did not influence the incidence of sodium channels There was no obvious association between voltage and the open probability of the channels Conclusions Our results indicate that most Na + channels in cell attached patches of human nasal epithelial cells are amiloride sensitive and Na + selective Only a few channels are amiloride insensitive The channels were not activated by extracellular Ca 2+ and the open probability followed a voltage independent manner

Mechanism of action of two insect toxins huwentoxin-Ⅲ and hainantoxin-Ⅵ on voltage-gated sodium channels

Selenocosmia huwena and Selenocosmia hainana are two tarantula species found in southern China.Their venoms contain abundant peptide toxins.Two new neurotoxic peptides,huwentoxin-Ⅲ(HWTX-Ⅲ) and hainantoxin-VI(HNTX-VI),were obtained from the venom using ion-exchange chromatography and reverse-phase high performance liquid chromatography(RP-HPLC).The mechanism of action of HWTX-Ⅲ and HNTX-VI on insect neuronal voltage-gated sodium channels(VGSCs) was studied via whole-cell patch clamp techniques.In a fashion similar to δ-atracotoxins,HNTX-VI can induce a slowdown of current inactivation of the VGSC and reduction in the peak of Na+ current in cockroach dorsal unpaired median(DUM) neurons.Meanwhile,10 μmol/L HNTX-IV caused a positive shift of steady-state inactivation of sodium channel.HWTX-ⅡI inhibited VGSCs on DUM neurons(concentration of toxin at half-maximal inhibition(IC50)≈1.106 μmol/L) in a way much similar to tetrodotoxin(TTX).HWTX-Ⅲ had no effect on the kinetics of activation and inactivation.The shift in the steady-state inactivation curve was distinct from other depressant spider toxins.The diverse effect and the mechanism of action of the two insect toxins illustrate the diverse biological activities of spider toxins and provide a fresh theoretical foundation to design and develop novel insecticides.

Effects of SO_(2)derivatives on sodium currents in acutely isolated rat hippocampal lead-exposed neurons

In this study, the effects of acute SO_2 derivatives and chronic lead exposure together on sodium cur-rents (INa) were investigated in acutely isolated rat hippocampal neurons by using the whole-cell patch clamp techniques. We found that chronic lead exposure hardly reduced the amplitudes of INa. In the normal condition, sodium current started to appear at around ?70 mV, and reached the peak current at around ?40 mV. After chronic lead exposure, the data changed to ?70 and ?30 mV. After adding SO2 derivatives, the data changed to ?80 and ?40 mV, respectively. SO_2 derivatives caused a significant in-crease of INa in hippocampal chronic-lead exposed neurons. Chronic lead exposure induced a right shift of the activation curve and a left shift of the inactivation curve of sodium channels. SO_2 derivatives caused negative shifts of the activation and inactivation curves of INa in hippocampal chronic-lead ex-posed neurons. Lead exposure put off the time reaching the peak of INa activation. SO_2 derivatives in-creased the time constants of inactivation after lead exposure. The interaction of lead and SO_2 deriva-tives with voltage-dependent sodium channels may lead to changes in electrical activity and contribute to worsening the neurotoxicological damage.

Lanthanum Chloride Promoted Proliferation with Enhanced S-phase Entry and Inhibited Potassium Currents of NIH 3T3 Cells

The effects of La^3＋ on proliferation, cell cycles, apoptosis and ion channels were investigated in mouse embryo fibroblast NIH 3T3 cells and its possible mechanisms were explored. Our data showed that La^3＋ promoted cell proliferation with increased S-phase entry and inhibited the outward potassium currents in a concentration-dependent manner in NIH 3T3 cells. La^3＋ and Ca^2＋ had synergistic effect on cell proliferation and cell cycles. It showed that Ca^2＋ was needed for La^3＋ promoted cell cycle progression. Using the whole-cell voltage-clamp technique, we found that La^3＋ blocked the outward potassium current in a Lanthanum ions can increase intracellular Ca^2＋ concentration concentration-dependent manner in NIH 3T3 cells. through inhibition of potassium currents, which induce a series of physiological changes and improve proliferation of cells. This may be one of the molecular mechanisms of lanthanum ions induced cell proliferation. The present work provides a new perspective for understanding the biological and toxicological effects of lanthanum.

Regulation of cardiac hERG potassium channel by protein tyrosine phosphatase non-receptor type 12, 11 and 6

Background Long QT syndrome(LQTS)is a potentially fatal cardiac ion channel disease.Mutations in the gene encoding cardiac hERG potassium channel are the second most common causes of LQTS.Cardiac hERG potassium channel conducts the rapidly activating delayed rectifier potassium current(Ikr),which is one of the crucial currents in rapid repolarization phase of action potential in human cardiomyocytes.Function of hERG potassium channel is regulated by a variety of signaling pathways,in which phosphorylation and dephosphorylation of tyrosine proteins plays a major role.Previous research has found that non-receptor protein tyrosine phosphatase(PTPN)can interact with hERG potassium channel in cardiac cells.The aims of the present study were to investigate the regulatory effect of protein tyrosine phosphatase non-receptor type 12,11 and 6(PTPN12,PTPN11 and PTPN6)on cardiac hERG potassium channels.Methods HEK-293 cells were transfected with pcDNA3.0-hERG by Lipofectamine 2000 and selected by G418.HEK-293/hERG cells stably expressing hERG protein were then transfected with pcDNA3.1-PTPN12-RFP,pcDNA3.1-PTPN11-EGFP and pcDNA3.1-PTPN6-EGFP,respectively.Forty-eight hours after transfection,immunofluorescence assay and western blot were performed to detect the expression of hERG channel proteins and PTPN proteins.hERG channel currents in hERG alone-expressing group,PTPN12-,PTPN11-and PTPN6-overexpressing groups,as well as inhibitor groups were recorded by patch clamp technique.Results The maximum pulse current densities of PTPN12-,PTPN11-and PTPN6-overexpressing groups were all decreased when compared with hERG alone-expressing group(P<0.05).However,the maximum pulse current densities of inhibitor groups were all increased when compared with PTPN12-,PTPN11-and PTPN6-overexpressing groups,respectively(P<0.05).Conclusions Overexpression of PTPN12,PTPN11 and PTPN6 reduced the current density of hERG potassium channel,while this effect could be reversed by tyrosine phosphatase inhibitors.These results suggested that PTPN12,PTPN11 and PTPN6 negatively regulated hERG potassium channel currents by catalyzing the dephosphorylation process of hERG potassium channels.[S Chin J Cardiol 2021;22(1):38-49]

Carvedilol Inhibits Na^+ Current in Rat Ventricular Myocytes

Objectives The effects of carvedilol on sodium current （INa） were investigated in isolated adult rat ventricular myocytes. Methods Single ventricular myocytes were enzymatically dissociated. INa was recorded by whole-cell patch- clamp recording technique. Results an IC50of （6. 35 - 0.40） mol . L^- 1. Carvedilol reversibly inhibited INa in a concentration-dependent manner, with 2. This inhibition was voltage- and frequency-dependent. 3. Carvedilol decreased the peak of the I-V relationship curve at -35 mV from （17.31± 1.68） pA/pF to （6. 58 ± 1.35） pA/pF, but did not change active potential, peak potential and the reverse potential significantly. 4. The steady-state inactivation curve of INa was shifted to more negative potentials. Conclusions Carvedilol inhibits INa in adult rat ventricular myocytes by mechanisms involving preferential interaction with the inactivated state of sodium channel.